Two ways, make the seller get rid of the bugs bedding, carpets and everything else or take it back under Magunson Moss and lawyer if need be.
Or get rid of the bugs mattresses furnishings and carpets yourself.
Can't find anyone then ask the Country Health Department what products to use to fumigate and spray with.
If you fumigate turn off the batteries and gas. Might help also to ten the underside with a sheet of poly taped around the lower exterior to ground, held down with bricks or something and bombs set off underneath. then bill the sell for all this or rather let your attorney.
I would ask a pest control company but they will tell you, you can't use the products they use and won't recommend anything generally. They want you to pay them of course.
Easiest except money wise is not to fool with the seller and choke it up.